The present specification relates generally to the field of integrated circuits and to methods of manufacturing integrated circuits. More particularly, the present specification relates to a cross-shaped resist dispensing system and method.
Generally, conventional integrated circuit manufacturing processes involve the transfer of geometric shapes on a mask to the surface of a semiconductor wafer or layer above the semiconductor wafer. The semiconductor wafer corresponding to the geometric shapes, or corresponding to the areas between the geometric shapes, is etched away. The transfer of the shapes from the mask to the semiconductor wafer typically involves a lithographic process. Conventional lithographic processes include applying a pre-polymer solution to the semiconductor wafer, the pre-polymer being selected to form a radiation-sensitive polymer which reacts when exposed to ultraviolet light, electron beams, x-rays, or ion beams. The solvent in the pre-polymer solution is removed by evaporation resulting from baking the pre-polymer film on the wafer. The film is exposed to radiation, such as, ultraviolet light, through a photomask supporting the desired geometric patterns.
The images in the photosensitive material are then developed by soaking the wafer in a developing solution. The exposed or unexposed areas are removed in the developing process, depending on the nature of the radiation-sensitive material. Then, the wafer is placed in an etching environment which etches away the areas not protected by the radiation-sensitive material. Due to their resistance to the etching process, the radiation sensitive-materials are also known as photoresists.
The high cost of photoresist pre-polymer solutions makes it desirable to devise methods of improving the efficiency of the coating process to minimize the amount of the polymer solution required to coat a substrate. Furthermore, thickness uniformity of the photoresist layer is an important criterion in the manufacture of integrated circuits. When the radiation is focused through the mask onto the coating, variations in thickness of the coating prevent the precise focus of the radiation over the entire surface of the wafer. Such precision is necessary to ensure satisfactory reproduction of the geometric patterns on the semiconductor wafer. Moreover, high precision is particularly important for advanced circuits with line width dimensions approaching 0.25 micron line widths and smaller.
Photoresist is often deposited to a substrate, or more particularly a wafer, by means of forming a puddle followed by spinning (i.e., spin coating). A large puddle of photoresist covering more than half of the substrate area is applied via a dispenser that directs a steady flow of resist in liquid form. The thickness on the puddle is on the order of a millimeter. The substrate is then spun at a speed ranging from 1,000 to 10,000 RPM to thoroughly spread out and remove the excess resist. This spinning results in a film thickness on the order of between a fraction of micrometer and a few micrometers. Therefore, only a small percentage of the photoresist material actually remains on the substrate. Most of the photoresist material dispensed is wasted, resulting in high cost and waste disposal problems.
In conventional systems, photoresist deposition utilizes a single pipe or a nozzle to dispense or spray coat the photoresist. Use of a single pipe or nozzle for photoresist deposition on a spinning wafer is taught in numerous patents, such as, U.S. Pat. Nos. 4,416,213; 5,254,367; 5,366,757; and 5,378,511. However, such conventional dispensing and spraying mechanisms use much more resist material than actually remains on the wafer. This inefficiency is costly, particularly due to the high cost of photoresist material.
Thus, there is a need to dispense photoresist material in a more efficient manner. Further, there is a need to dispense photoresist material that limits waste and increases uniformity of the dispensed photoresist material. Yet further, there is a need for a cross-shaped resist dispensing system and method.
An exemplary embodiment is related to a method of depositing photoresist material on an integrated circuit wafer. This method can include providing a cross-shaped resist dispenser including a plurality of resist dispense nozzles; dispensing photoresist material through the plurality of resist dispense nozzles to an integrated circuit wafer; and rotating at least one of the cross-shaped resist dispenser and the integrated circuit wafer.
Another exemplary embodiment is related to a method resist dispensing system used in the dispensing of photoresist material on a wafer in an integrated circuit fabrication process. This system can include a wafer supporting structure which supports a wafer; and a cross-shaped platter having a plurality of dispensing nozzles for dispensing resist material on the wafer.
Another embodiment is related to an apparatus for coating a substrate with a soluble material. This apparatus can include a spin chamber; a cross-shaped dispenser located in the spin chamber, the cross-shaped dispenser having a plurality of dispensing nozzles; a substrate support which locates a substrate within a proximity distance of the cross-shaped dispenser; and means for spinning the substrate such that the soluble material is distributed about the substrate.
Other principle features and advantages of the present invention will become apparent to those skilled in the art upon review of the following drawings, the detailed description, and the appended claims.